1. Field of the Invention
The invention concerns apparatus for shock wave treatment including an ultrasonic shock wave transducer having a delay path filled with an acoustic coupling medium enclosed by a membrane which is arranged to be placed on the body of a patient to be treated by means of shock waves generated by the transducer. The invention relates in particular to an X-ray device in such apparatus, for locating a concretion or tissue in the patient's body, to be destroyed by the shock waves, the device comprising an X-ray source having a tube which can be filled with an X-ray loss-free medium, for example a gas, and being arranged within the delay path and sealed against the coupling medium.
2. Description of the Related Art
Such apparatus have two location finding devices for finding the location of a concretion or tissue, namely an ultrasonic location finding device and an X-ray location finding device which extend through the cup-shaped body of the shock wave transducer, and into the delay path thereof. The tube is closed at its end facing the membrane. The tube and a balloon are sealed against the coupling medium of the delay path and can be filled with a gas, for example air, so as to cause as little absorption as possible of the X-rays. During operation, the tube and the balloon are filled with gas in such a way that the balloon expands and comes to rest against the inner side of the membrane and thus indirectly against the body of the patient to be treated, so that the liquid coupling medium within the delay path which is strongly X-ray absorbent is almost completely displaced from the path of the X-rays.
The location of the concretion or tissues by X-rays is considerably improved because the X-rays pass through the gas and are, therefore, subjected to substantially less absorption than would be the case if they were to pass through the coupling medium which is a liquid. The tube however, being of sufficient length to enable efficient X-ray location, causes fade out of a relatively large part of the sonic field of the shock wave transducer. Such fade out is also caused by the balloon. Thus to shorten the tube whilst correspondingly enlarging the balloon would not serve to avoid fade out of the sonic field, because for X-ray location finding, the balloon must be expanded to such an extent that it can no longer adapt to the X-ray cone and so fades out a substantial part of the sonic field. Such fading out of the sonic field can affect the efficiency of shock wave therapy.